The present invention relates to a vehicle motion control device that controls a pressure (hereinafter, referred to as “W/C pressure”) generated in a wheel cylinder (hereinafter, referred to as “W/C”) based on a motion condition in a lateral direction of a vehicle so as to suppress a roll of the vehicle.
JP-A-2001-219840 discloses a system that can control the rolling stability of a vehicle. In the system, if a lateral acceleration is generated at the time of turning, understeering is generated to cause lateral sliding by increasing the braking force of a turning-outside front wheel so that a greater difference in braking force is generated between the right and left wheels as the roll angle becomes greater than a threshold value, and causing a yaw torque. Accordingly, the rolling stability is controlled so that a vehicle does not roll by decreasing the roll angle of the vehicle using the reverse lateral acceleration generated with the understeering in the meantime.
However, since it is not necessary to generate understeering any more in a situation where great understeering is already generated or a situation where a driver returns the steering wheel, it is not preferable that the increase in braking force of the turning-outside front wheel is continuously maintained.
In a generic car, the lateral sliding is caused by generating the understeering is effective. However, in a large-sized vehicle such as a truck, if a braking force is given to the turning-outside front wheel by employing the above-mentioned control, a pitching phenomenon about the turning-outside front wheel, that is, a phenomenon that a nosedive (a state where the vehicle body is inclined forward) is caused about the turning-outside front wheel, may occur without causing the intended lateral sliding, in addition to the phenomena that the forward or backward movement of weight increases, the lateral sliding does not therefore occur properly, and the roll angle at the time of turning early increases.